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  1. #1
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    Default Help with insulating exterior walls

    I have come to understand, from a local "old house" guru, that the blown in insulation is very damaging to wood siding (and structure) if you do not have a vapor barrier. I am looking to use a spray foam to insulate my plaster exterior walls on my 1914 Craftsman home. Is this a good product
    http://www.tigerfoam.com/index.php
    and, does the "closed cell" foam prevent the moisture problems associated with the regular blown in insulation?\

    Thanks for your help/suggestions!

  2. #2
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    Default Re: Help with insulating exterior walls

    SCampbell ... perhaps you could explain what the "moisture problems associated with the regular blown in insulation"

  3. #3
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    Default Re: Help with insulating exterior walls

    yes, I will elaborate.

    warm, moist air vapor in our homes created by cooking, taking showers, having house plants, breathing, etc. is attracted to the exterior walls and the vapor enters the wall through hairline cracks, outlets, switches, and window trim. With no vapor barrier, the wet air hits the insulation and condenses. This wets down the blown in insulation and makes it a wet mess at the bottom of the wall cavity creating an inviting place for termites and dry rot. Then the moisture enters the exterior sheathing and wood siding causing permanent exterior paint failure. Then, if you add vinyl siding, you now have an impermeable vapor barrier on the outside, thus stopping the free exchange of air, trapping the moisture, and ruining your home. Now you see my predicament.

  4. #4
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    Default Re: Help with insulating exterior walls

    Scampbell …. Thanks for elaborating.

    I would have to agree in part to some things you mentioned.
    Yes … warm humid air can leak into the wall cavity through things like switches and receptacles and likely condense. This would likely be when the outside temperature is at or below freezing in which case this condensation would freeze inside the wall cavity and is benign in this form. When the temperature warmed enough to thaw this moisture it would “breathe out through the exterior siding … as you mentioned. This is the way millions of homes across North America have existed for decades and with not as much impact as you describe. That’s one reason to try and seal things from the inside.

    To describe a wet mess of insulation from the humidity passing through the walls … sure it’s possible ... however I really haven’t seen much of this being sever or really being an issue.
    Such is the case of my own home built in 1953 which is being renovated ( slowly mind you). There is plenty of leakage from the interior spaces in 55 years and I haven’t run across anything that nears what you have described including having the vinyl siding added to the exterior some years ago.
    More often evidence of rot due to moisture is usually from water infiltration from rain or melting snow or ice getting into the wall cavity or from the inside space like bathrooms.
    Adding vinyl siding isn’t a completely sealed monolithic covering … so not being completely air tight there will still be some “breathing” happening behind the vinyl.

    Regardless of whatever type of insulation is used if moisture was allowed to penetrate the wall cavity it could still do what you describe … even closed cell spray foam. In an extreme situation as you suggest…. moisture is not absorbed by the spray foam therefore it would simply trickle downward to the bottom of the wall cavity and accumulate there.

    Food for thought.

  5. #5
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    Default Re: Help with insulating exterior walls

    Quote Originally Posted by canuk View Post
    Regardless of whatever type of insulation is used if moisture was allowed to penetrate the wall cavity it could still do what you describe … even closed cell spray foam. In an extreme situation as you suggest…. moisture is not absorbed by the spray foam therefore it would simply trickle downward to the bottom of the wall cavity and accumulate there. Food for thought.
    Food for mold & rot, not thought!

    That condensation is going to occur anytime dew point is reached, not just when outside temperatures are at or near freezing! Rotting sill plate, wall studs, mold, etc.

    Consult someone who knows, obviously canuk doesn't.
    Last edited by unregistered; 02-12-2008 at 12:26 AM.

  6. #6
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    Default Re: Help with insulating exterior walls

    unregistered wrote :

    Consult someone who knows, obviously canuk doesn't.
    Well look who's back to their old form ... it was just a matter of time.

    Instead of your personal attack campaign ..... how about if you offer some helpful advice.
    Last edited by canuk; 02-12-2008 at 08:41 AM.

  7. #7
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    Default Re: Help with insulating exterior walls

    Quote Originally Posted by canuk View Post
    This would likely be when the outside temperature is at or below freezing in which case this condensation would freeze inside the wall cavity and is benign in this form.
    Mold, mildew, wood rot, rust are still active at freezing temperatures.

    Water expands when frozen. Water-logged materials (foundation plate, wood, fastener materials, etc.) when frozen/heaving can suffer damages.

  8. #8
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    Default Re: Help with insulating exterior walls

    Quote Originally Posted by Shaun 007 View Post
    Mildew fungi are dormant at freezing temps .
    And like Neil Young says ...Rust Never Sleeps.

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